Carrier sense multiple access (Carrier Sense Multiple Access, CSMA) is a distributed medium access control protocol. Each site (node) in a network competes to send a data frame by using a CSMA time slot. FIG. 1 is a network architecture diagram of a typical communication network. As shown in FIG. 1, a concentrator, level-1 sites, level-2 sites, and level-3 sites that request to access the level-2 sites are included. In an ad hoc networking stage, the concentrator allocates a CSMA time slot, that is, carries a CSMA time slot shared by all the sites to upload data in a beacon frame, and delivers the beacon frame to the level-2 sites. All the level-3 sites obtain the CSMA time slot and perform carrier sensing, and can send an access-request packet to the level-2 sites that are requested to be accessed only when the CSMA time slot is idle.
It can be seen that, when the concentrator provides a CSMA time slot for the network sites in the foregoing manner, all the level-3 sites share the CSMA time slot, and when there are multiple level-3 sites requesting for access, it cannot be known and managed in advance that which level-3 site (level-3 sites) can successfully send an access-request packet to take priority to access the concentrator in the network. However, in some actual application scenarios, the concentrator expects to designate, according to a certain rule, level-3 sites having different time slots to access in different periods, for example, a level-3 site that accesses a certain designated level-2 site; therefore, when a CSMA time slot is provided, an applicable site of the CSMA time slot needs to be designated. However, a current CSMA time slot providing method cannot designate an applicable site of the CSMA time slot.